Lubricating oil composition



United States Patent-O P 3,014,870 W LUBRICATING'OIL COMPOSITION William W. Reynolds and Hans Low, East Alton, Ill.,

assignors to Shell Oil Company, a corporation of Delaware No Drawing. Filed Oct. 29, 1959, Ser. No. 849,454 2 Claims. (Cl. 252-496) This invention relates to improved lubricating oil compositions, and more particularly, to mineral lubricating oil compositions which are resistant to oxidative deterioration under storage or use in equipment subjected to adverse operating conditions of temperature and pressure.

Lubricating oils such as mineral oils in the lubricating viscosity range tend to deteriorate and break down due to oxidation both in storage and during use, particularly at extremely high temperatures, such as above 400 F. and higher, resulting in the formation of undesirable products such as gums, sludges, resins, acidic products and other deleterious products which decrease the useful life of the oil or render it useless Within a short period of time. Mineral oils'of this type include aircraft, truck and automobile mineral lubricating oils, industrial oils such as gear oils, transformer oils, hydraulic oils and the like.

It is known that certain aromatic amines are useful as oxidation inhibitors for mineral oils. However, their application is limited because of their tendency to discolor mineral oils and form deposits particularly at elevated temperatures. Other types of anti-oxidants such as alkyl phenols, such as diand trialkyl-phenols, e.g., 2,4-diamylphenol and 2,6-ditert-butyl-4-methylphenol are eifective only in certain types of mineral oil and are oxidatively unstable at elevated temperatures.

It is an object of this invention to inhibit or prevent oxidation of mineral oil. Still another object is to inhibit or prevent deterioration, discoloration and deposit formation in mineral oil during storage and use over a wide temperature range, particularly at elevated temperatures. Other objects of the invention will be apparent from the following description of the invention.

It has now been discovered that various types of mineral lubricating oil including those which contain substantial amounts of aromatic (5-30%) can be effectively stabilized even at temperatures above 400 F. without undesirable side etfects by addition thereto of small amounts (0.052%, preferably 0.l-l% by Weight) each of an I oil-soluble aromatic amine having the Formula I RR NH,

wherein the Rs are the same or diflerent monoor diaromatic radicals, and an oil-soluble boron compound having at least one OH group and at least one R-B linkage where R is an oil-solubilizing hydrocarbyl radical having at least 6 carbon atoms. Compounds of this type include hydrocarbon boronic acid, RB(OH) or its monoester where R is preferably an alkyl radical of at least 12 carbon atoms and R is an alkyl, aryl or cycloalkyl radical of at least 6 carbon atoms. The C1248 alkyl boronic acids are preferred. s

The oil-soluble aromatic amines represented by Formula I include diphenyl, dinaphthyl, phenyl alpha-naphthyl, phenyl beta-naphthyl amines and mixtures thereof.

01 ,870 Patented Dec. 26, 196 1 Icev 1 a viscosity range of from 50 SUS at 100 F. to 250 SUS The above B-hydrocarbyl boronic compounds can be 1909, as well as by the method described by Groszos' in U.S. Patents 2,862,952 and 2,884,441.

at 210 F. A typical useful oil is a refined mineral lubricating oil (X) having the following properties:

Pour point, F. 29-31 Flash point, F. (COC) Min. 420 Viscosity SUS, F 345-355 Unsulfonated residue Min. 98

Another typical useful oil (Y) isan Oklahoma neutral petroleum fraction having the following properties:

Specific gravity 0.876 Pour point, F. +10 Viscosity at 100 F., cs 56.88 V.I 93.9 Flash point, COC, F. 450 Fire point, F. 490 Aromatics, percent 23.7

To illustrate the pronounced superiority of the additive combination in stabilizing and preventing oxidation of mineral oil, the following compositions were prepared and evaluated in a micro-oxidation test of the MIL-L- 7-808 oxidation test under the following test condition: air flow of 1 liter/hour oxidizing agent, 400 F., solid metal catalyst (Ag, Ti, Cu, Mg, Fe), with the results as shown in Table I.

Table l [Base=refi.ned mineral lubricating oil X, amount of inhibitor=0.0=M= 0.002 mole/100 g.]

Hours to Adsorb l millimole Oz/g. oil

Inhibitor (1) None 11 (2) Phenyl-alpha-naphthylamine 8 (3) Beta-beta-dinaphthylamine 17 6 (4) Diphenylamine 4 (5) Dodecyl boronic acid". 6 2+5 Other compositions of this invention which would be expected to give comparable results to composition 6, Table I of this invention, include:

(7) Mineral oil X+0.02 M phenyl-alpha-naphthylamine +0.02 M octadecyl boronic acid,

(8) Mineral oil X+0.02 M beta,beta-dinaphthylamine +0.02 M octadecyl boronic acid,

(9) Mineral oil X+0.02 M phenyl-alpha-naphthylamine +0.03 M 3,3,5-triethyl cyclohexyl boronic acid,

(10) Mineral oil+0.02 M phenyl-alpha-naphthylamine 0 +0.02 M monomethyl dodecyl acid boronate.

' The additive combination of this invention can be used in neat mineraloils or with mineral oil compositions which contain pour point depressants, viscosity index improvers, corrosion inhibitors, detergents and the like.

We claim as our invention: I

l. A mineral lubricating oil composition consisting essentially of a major amount of mineral lubricating oil and from about 0.05 to about 2% each of an oil-soluble aromatic amine selected from the group consisting of phenyl-alpha-naphthylarnine and beta,beta-dinaphthy1- amine and an oil-soluble B-hydrocarbon substituted boron compound selected from the group consisting of dodecyl boronic acid, oetadecyl boronic acid, 3,3,5-triethyl cyclohexyl boronic acid, and monomethyl dodecyl acid boronate.

2. A mineral lubricating oil containing from about 0.05% to about 2% each of phenyl-alpha-naphthylamine and dodecyl boronic acid.

References Cited in the file of this patent UNITED STATES PATENTS 

1. A MINERAL LUBRICATING OIL COMPOSITION CONSISTING ESSENTIALLY OF A MAJOR AMOUNT OF MINERAL LUBRICATING OIL AND FROM ABOUT 0.05 TO ABOUT 2% EACH OF AN OIL-SOLUBLE AROMATIC AMINE SELECTED FROM THE GROUP CONSISTING OF PHENYL-ALPHA-NAPHTHYLAMINE AND BETA,BETA-DINAPHTHYLAMINE AND AN OIL-SOLUBLE B-HYDROCARBON SUBSTITUTED BORON COMPOUND SELECTED FROM THE GROUP CONSISTING OF DODECYL BORONIC ACID, OCTADECYL BORONIC ACID, 3,3,5-TRIETHYL CYCLOHEXYL BORONIC ACID, AND MONOMETHYL DODECYL ACID BORONATE. 